Electropolishing of drilled surgical needles

ABSTRACT

A LARGE NUMBER OF STEEL SURGICAL NEEDLES ARE SUPPORTED IN A MAGNETIC FIELD ON A PLATINUM, PALLADIUM, RHODIUM, IRIDIUM, OR GOLD ANODE THAT IS IMMERSED IN A MAGNETIC ELECTROPOLISHING BATH. THE NEEDLES SUPPORTED ON THE ANODE ARE POLISHED BY A CURRENT THAT FLOWS THROUGH THE SOLUTION AND NEEDLES TO PRODUCE A SMOOTH NEEDLE SURFACE THAT IS FREE OF FLAWS AT THE POINT OF CONTACT WITH OTHER NEEDLES ON THE ANODE.

NOV. 21,1972 I BERQFF ETAL ELECTROPOLISHING OF DRILLED SURGICAL NEEDLESFmdJan. 27,1972

4 SheetsSheet 1 Nov. 21,1972 H. BEROFF ETAL 3,703,452

ELECTROPOLISHING OF DRILLED SURGICAL NEEDLES Filed Jan. 27, 1972 4Sheets-Sheet a ELEGTROPOLISHING 0F DRILLED SURGICAL NEEDLES Filed Jan.27, 1972' NOWILJQ'TZ BERQFF ETAL 4 Sheets-Sheet 3 rlllL ELECTROPOLISHINGOF DRILLED SURGICAL NEEDLES Filed Jan. 27, 1972 H. BEROFF ET AL Nov.21,1972

4 Sheets-Sheet 4.

United States Patent 3,703,452 ELECTROPOLISHING OF DRILLED SURGICALNEEDLES Howard Beroif, Somerville, and Ernest L. Richmond, NorthPlainfield, N.J., assignors to Ethicon, Inc. Continuation-impart ofapplication Ser. No. 6,878, Jan. 29, 1970. This application Jan. 27,1972, Ser.

Int. Cl. C23b 3/06', 5/70; B23p 1/10 US. Cl. 204-129.1 12 ClaimsABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This patentapplication is a continuation-in-part of copending, commonly-assignedpatent application, Ser. No. 6,878, filed Jan. 29, 1970, and nowabandoned.

The present invention relates to the electropolishing of surgicalneedles and more particularly to an improved apparatus for theelectropolishing of drilled stainless steel needles. The needlesproduced by the apparatus of the present invention are free of scale,discoloration, and gross surface imperfections and have a mirror-likefinish.

In the modern operating room there is available to the operating surgeona variety of suture materials having affixed to one end thereof asurgical needle of the proper size and shape for the operation inprogress. Thus, hundreds of thousands of surgical needles may be usedevery day in hospitals throughout the United States and are discardedafter use to insure sharpness and to avoid the problems ofresterilization.

Surgical needles are generally formed of stainless steel in order toresist the corrosion that may occur during storage in the tubing fluid.A preferred form of needle is a drilled needle, which has a concentriccylindrical hole drilled in the blunt end of the needle. Such needlesare formed from stainless steel wire which is straightened and cut toform a blank, one end of which is then dieformed to produce a cuttingedge or point. The cutting edges are then ground until sharp. Finally,the needle is formed to the desired shape and heat treated to improvethe temper (increase the hardness of the needle without impairingbrittleness). During this heat treatment step, the needles willfrequently become discolored with a coating of oxide or scale that isremoved in the polishing process.

It is well known among those skilled in the art of needle making thatsurgical needles subsequent to sharpening and tempering may be polishedelectrolytically by immersing the needle in an acid solution and passinga direct current through the solution and the needle being polished. Thescale and discoloration that may result from the heat treatment isthereby removed and the needle is polished in that small surfaceimperfections are removed by anodic dissolution of metal. Theelectropolishing of surgical needles has always been an expensive andtime consuming process, however, because it was necessary to exercisegreat care in supporting the needle within the polishing bath. Onemethod of supporting the needles during the polishing step uses amagnetic needle rack as described in United States Pat. No. 3,268,428.It is a disadvantage of the magnetic rack described in that pat-3,703,452 Patented Nov. 21, 1972 cut, however, that the precisepositioning of the needle on the face of the magnet is a time consuminghand operation.

Another method of supporting surgical needles Within the electrolyticpolishing bath that has been used by the assignee of the presentapplication in the manufacture of surgical needles was to secure thedrilled end of the needle in a conductive metal clip. The needle is thenplaced below the surface of the electropolishing bath so that the entireneedle surface is polished, except for the drilled end which contactsthe clip. Again, however, a time consuming operation is involved sinceeach individual needle must be precisely placed in its correspondingsupporting clip so that the clip contacts the needle surface only at itsremote drilled end. This precaution is necessary because the needle willbe etched and roughened at the point of contact with its supportingclip. By supporting the needle at the butt and such imperfections are ofminimum concern since the marks made during the electropolishing stepare generally obscured during the swaging of the drilled needle to thesuture material.

It has now been discovered that stainless steel surgical needles may beelectropolished in large batches by placing a substantial number of suchneedles in an electrolytic fluid on a platinum, palladium, rhodium,iridium or gold polishing anode in random arrangement. The steel needlesare held against the surface of the anode by magnetic force. While onewould have expected that needles polished in this manner would havesurface imperfections and cross-over marks on those areas in contactwith adjacent needles during the polishing step, this did not occur. Theprocess to be described reduces the time that is required for polishingsince it is unnecessary to handle each individual needle. Moreover, itis possible to control the process to be described so accurately thatless than 0.0005 inch of material is removed. Inasmuch as the diameterof surgical needles is controlled to within 0.001 inch, it is nowpossible for the first time to repolish a needle that retains a slightsurface imperfection without removing more than the 0.001 inch permittedby quality control specifications. The object of the invention,therefore, is to provide a fast and reliable method for polishing aplurality of stainless steel needles in large batches whereby scale andsurface imperfections that are present following the heat treating stepare removed to provide a bright uniformly polished surface that isdevoid of cross-over marks.

The foregoing object may be attained in accordance with the presentinvention which provides a novel electropolishing apparatus comprisingan anode that is rectangular in cross-section having a magnetic centralcore. The central core has a titanium metal frame to which is secured aplurality of small ceramic magnets. The magnets serve the importantfunction of retaining the needles to be polished in electrical contactwith the surface of the anode and each other, and are part of a hingedassembly which permits the operator to discharge the needles after thepolishing operation by swinging the surface of the anode and the needlessupported thereon out of the magnetic field.

The apparatus of the present invention permits one to polish a largebatch of needles, i.e., 200 to 3,000 at one time, depending upon thesize of the needles. The needles to be polished may be scattered overthe anode surface from a large container and discharged from the anodewithout the tedious and time-consuming hand operations formerlyemployed.

The polishing anode is designed for the rapid polishing of surgicalneedles and its construction is such that the needles contact only theexterior surfaces of the anode and each other. It has been discoveredthat a platinum, palladium, rhodium, iridium or gold surface is requiredto obtain the desired mirror-like polish on the needles. Other materialsinvestigated did not produce polished needles of the same quality. Thesurface of the anode that contacts the needle to be polished must resistetching by the electropolishing bath throughout the polishing process.Moreover, the metal used for the anode must be one that does not form asurface coating during the use that will interfere with theelectropolishing operation. Most metals that might otherwise be used forforming the polishing anode surface either dissolve in theelectropolishing bath or form a surface coating during the electropolishing process that results in needles of inferior quality.

Particularly preferred as the anode surface is platinum gauze (No. 80United States Standard Sieve Series, 177 micron). Alternatively, atitanium anode the surface of which is plated with platinum (mattefinish) or a sheet of gold, palladium, rhodium, or iridium about 0.010inch in thickness may be used.

The invention will appear more clearly from the following detaileddescription when taken in connection with the accompanying drawings,which show by Way of example, preferred embodiments of the inventiveidea. Referring now to the drawings:

FIG. 1 is a perspective of the apparatus.

FIG. 2 shows a vertical cross-section of the unloading tray andassociated parts, taken along line 2-2 of FIG. 1.

FIG. 3 is a vertical cross-section through the electrolytic bath takenon line 3-3 of FIG. 1.

FIG. 4 is an enlarged cross-section partly in elevation through one ofthe cathode plates and taken along line 44 of FIG. 3.

FIG. 5 shows a vertical cross-section of the wash tank taken along line5-5 of FIG. 1.

FIG. 6 is a vertical face or elevational view of a magnetic tray unit;broken away in a cross-section. The righthand side being in elevationand broken away to see the screen, titanium plate, and the grillportions beyond which the fixed magnet unit is seen.

FIG. 7 is an inverted fragmental edge elevation of FIG. 6 partly insection and partly in elevation,

FIG. 8 is an end elevation, broken away and in section of the left sideof FIG. 6 showing only the centrally located magnet unit.

FIG. 9 shows a perspective of one of the magnets shown in FIGS. 6 to 9.

FIG. 10 is an enlarged cross-section taken along line 10-10 of FIG. 6showing the laminated structures hingeable at their upper ends, and

FIG. 11 is an exploded perspective of the laminations shown in FIG. 10.

The construction of the anode assembly is best shown in FIGS. 6 through11. In the embodiment illustrated, the conductive metals used to buildthe assembly are platinum, which forms the surface of the anode, andtitanium. It has been found that titanium quickly forms a titanium oxidesurface coating under the conditions of use that is highly resistant tocurrent flow. This greatly increases the efficiency of the polishingoperation, and reduces the temperature rise of the electropolishing bathsince the primary current flow is through the needles 17 being polishedand the platinum support. There is very little current leakage throughthe titanium oxide surface of the anode assembly.

The magnetic field that retains the needles against the anode surfaceduring the polishing operation may be pro vided by a plurality of smallrectangular, permane n't magnets best illustrated in FIG. 10. If theconstruction of the anode is such that the magnets are in contact withthe electropolishing bath suitable non-conductive ceramic magnets may beobtained from Indiana General Corporation, Valparaiso, Ind. (INDOX 5).Shallow transverse channels 16 and 16' are provided in the magnetsurfaces to facilitate clamping the magnet to a central frame 18 which,together with a plurality of magnets 15, form the magnetic core 19 ofthe anode assembly.

The magnetic core 19 is best illustrated in FIGS. 6 through 8. Itconsists of the frame 18 that is rectangular in shape; the outerdimensions being fixed by the end members 20 and 20 and the longitudinalmembers 21 and 21'. Extruding outwardly from the lower frame member, asviewed in FIG. '6, are cylindrical pintles 22 and 22, the function ofwhich will be described below. The frame is divided by cross-bars 23 andlongitudinal bars 24 into a series of compartments, the dimensions ofwhich correspond to the length and width of magnet 15. The magnets areoriented in the frame so that the north pole of each magnet is inproximity with the south pole of every adjacent magnet and are firmlysecured in position by the clamping bars 26 and 26' which engage thechannels 16 and 16' in the magnets 15 and are secured to the framemembers 21 and 21' by screws 27 and 27'.

The top member 21' of the frame 18 is welded to vertical supports 29that suspend the entire anode assembly from a bus bar 30.

A handle 31 is attached to the top of the bus bar and facilitatesaccurate positioning of the anode assembly in the electropolishing bath.

To complete the description of the anode there is positioned on bothsides of the magnetic core assembly described above platinum screens 32and 32' slightly greater in length and breadth than the frame 18.

The platinum screen 32 and a backing sheet of titanium 33, are heldbetween a grill 34 and an outer frame by the bolts 36 which engagethreads in the grill 34. In a like manner, the platinum screen 32' andits backing sheet 33 are held between the girll 34 and outer frame 35 bythe bolts 36 which engage threads in the grill 34. The platinum screensurfaces and their supporting frame are hinged by means of hinge pins 37and hinge brackets 38 to the vertical members 29 which support theentire electropolishing anode assembly and function to conduct currentto the anode during the electropolishing operation. Small ceramicmagnets 39 are mounted on the lower edge of the grills 34 and 34'. Thesemagnets act to hold the grills 34 and 34' together so that the platinumscreens are parallel to each other and to the magnetic core assemblyformed by the inner frame 18, magnets 15 and clamping bars 26.

Inasmuch as the ceramic magnets are corroded by the acidelectropolishing bath and have a limited commercial life, a preferredembodiment of the present invention is to encapsulate the magnetic corewithin a titanium container, welding all joints to prevent contactbetween the electropolishing bath and the magnets.

Example 1.Electropolishing of drilled /z circle stainless steel surgicalneedles As best shown in FIGS. 1 and 2, the magnetic anode describedabove having a dual surface area of about 200 square inches is supportedon a work table 40 with the pintles 22 and 22' positioned between guideposts 41 and 41 above a catch screen 42 and a weighed quantity of thesurgical needles 17 to be polished (about 350 needles; diameter 0.039inch) is distributed evently over the platinum surface 32 of the anode.The anode is then rotated toward the operator on the pintles 22 and 22',to the position shown in dotted lines in FIG. 2. The anode in thatposition is supported on the tray rests 43 and 43' with the othersurface of the anode 32' facing upward. The needles on the lower surface32 are retained by magnetic attraction.

An equal weight of surgical needles is evenly distributed in like mannerover the opposite surface. The magnetic anode with the needles in placeis then removed from the work table and placed in an electropolishingbath 44 between two cathodes 45 and 46. The two cathodes are similarlyconstructed of stainless steel as best illustrated in FIGS. 3 and 4.Individual separated cathode plates 51 are secured to the cathode busbar '53 by bolts 55 and 55 and extend across a ceramic vat 48equidistant from the platinum surfaces 32 and 32 of the polishing anode.As best illustrated in FIG. 1, the magnetic anode makes electricalcontact with the polishing tank bus bar 50.

The electropolishing bath is a solution containing 70 parts by weight orthophosphoric acid, 30 parts by weight hydroxyacetic acid. Thiselectropolishing solution is contained in the ceramic vat 48.

Current is passed through the polishing bath and needles for 4 minutes.The current flow is 72 amperes at volts, and the temperature of thepolishing bath is 190 F. A DC rectifier that will supply 100 amperes at12 volts is suitable as a power supply. Fumes and vapors from theelectropolishing bath are carried away by the exhaust duct 65.

After polishing for 4 minutes, the anode is removed from the polishingbath and placed on the rest ledges 49 and 49" over the polishing bath topermit the acid polishing solution to drain from the needles and anode.The anode is then transferred to a first water rinse compartment 52 of afour-station rinse tank 54. The anode and needles are rinsed in thecompartment 52 for 1 minute and then transferred to the second rinsecompartment 56 for another minute to flush off any remaining polishingacid. The rinse tanks are continuously supplied with water through inletvalves 57 at a rate of 1 gallon per minute; and overflows through theexit ports 59; the temperature of the rinse water being maintained at115 F.

After the water rinses, the anode is advanced to a third compartment '58where the needles are submerged in a solution ocntaining 183 parts byvolume orthophosphoric acid, reagent grade; 20 parts by volume of awetting agent (Triton X-100); and 6725 parts by volume water. Thissolution acts to complex any iron carried over from the polishing stepand prevents discoloration of the needles. The needles are then advancedfrom the phosphoric acid solution to a final water rinse compartment 60,continuously supplied with warm water at the rate of 1 gallon perminute.

The anode together with the partially polished needles is then removedfrom the tank and supported over the drain 61 at the end of the tank 54as shown in FIG. 5. After draining, the anode is placed over anabsorbent paper towel and the platinum surface 32 is swung about thehinge pin 37 away from the magnetic core permitting the needles to droponto the paper towel. In a similar manner, the needles on the platinumsurface 32' may be collected.

The platinum screens of the anode assembly are repositioned over themagnetic core and the anode is replaced on the work table in positionfor loading. The partially polished needles are returned to the anodesurfaces and evenly distributed as described above. The anode with theneedles in place is then reinserted in the electropolishing bath andpolished for an additional 3 minutes as described above. During thissecond polishing cycle the current flow is 70 amperes at 10 volts. Theanode is removed from the polishing bath; the needles are rinsed withwater, treated with phosphoric acid solution, and washed exactly asdescribed above.

After draining ,the needles may be transferred to a fiber board traylined with paper towels by swinging the platinum surfaces away from themagnetic core of the anode assembly. The needles in the fiber board trayare then passed over a 60 cycle alternating current magnet until theneedles in the tray lay fiat indicating that no residual polarityremains.

Needles polished as described above upon inspection are found to have amirror-like surface free of cross-over marks and other imperfections.The electropolishing process removes about 0.001 inch, i.e., a needle0.039 inch in diameter before polishing will measure about 0.038 inch indiameter after polishing.

Similar results may be obtained by substituting a thin sheet of platinumfor the platinum screens 32 and 32. Drilled one-half circle stainlesssteel needles (diameter 0.028 inch) may be successfully polished by themethod described above. These smaller needles (650) 'were distributedevenly over the platinum surface of the anode. The total number of suchneedles polished at one time is about 1300.

Example II.--Electropolishing of drilled circle stainless steel surgicalneedles About 1300 needles (diameter 0.026 inch) are polished by theprocedure described in Example I above. The anode surfaces 32 and 32 aregold sheets 0.10 inch in thickness. The needles are randomly distributedover both anode surfaces (about 650 needles per side). Upon inspection,the needles so polished were found to have a mirror-like surface free ofcross-over marks and other imperfections.

Example III.-Electropolishing of drilled circle stainless steel surgicalneedles About 1200 needles (diameter 0.028 inch) are polished by theprocedure described in Example I above. The anode surfaces 32 and 32'are palladium sheets 0.10 inch in thickness. The needles are randomlydistributed over both anode surfaces (about 600 needles per side). Uponinspection, the needles so polished were found to have a mirrorlikesurface free of cross-over marks and other imperfections.

Example IV.-Electropolishing of drilled circle stainless steel surgicalneedles About 900 needles (diameter 0.032 inch) are polished by theprocedure described in Example I above. The anode surfaces 32 and 32'are rhodium sheets 0.10 inch in thickness. The needles are randomlydistributed over both anode surfaces (about 450 needles per side). Uponinspection, the needles so polished were found to have a mirror-likesurface free of cross-over marks and other imperfections.

Example V.-Electropolishing of drilled A; circle stainless steelsurgical needles About 800 needles (diameter 0.039 inch) are polished bythe procedure described in Example I above. The anode surfaces 30 and 32are iridium sheets 0.10 inch in thickness. The needles are randomlydistributed over both anode surfaces (about 650 needles per side). Uponinspection, the needles so polished were found to have a mirror-likesurface free of cross-over marks and other imperfections.

While the invention has been described in detail according to thepreferred manner of carrying out the process and manufacturing theproducts, it will be obvious to those skilled in the art, afterunderstanding the invention, that changes and modifications may be madetherein without departing from the spirit or scope of the invention, andit is intended in the appended claims to cover such changes andmodifications.

What is claimed is:

1. A method for electropolishing a batch of surgical needles whichcomprises:

supporting a large number of randomly oriented needles in a magneticfield on a platinum anode; immersing said anode and needles supportedthereon in an electropolishing bath;

passing an electric current through the polishing bath and needles untilthe needles are polished;

removing the anode and the needles supported thereon from said polishingbath; rinsing the needles;

removing the needles from the anode; and,

subsequently drying the polished needles.

'2. The method of claim 1 wherein said anode is a sheet of platinumgauze.

3. The method of claim 1 wherein said anode is constructed of titaniumat least one surface of which is coated with platinum.

4. The method of claim 1 wherein said needles prior to the drying stepare replaced in a random manner on the anode; immersed a second time inthe electropolishing bath; and the polishing and rinsing steps arerepeated, after which the polished needles are dried.

5. A method for electropolishing a batch of surgical needles whichcomprises:

supporting a large number of randomly oriented needles in a magneticfield on a gold anode; immersing said anode and needles supportedthereon in an electropolishing bath;

passing an electric current through the polishing bath and needles untilthe needles are polished;

removing the anode and the needles supported thereon from said polishingbath;

rinsing the needles;

removing the needles from the anode; and,

subsequently drying the polished needles.

6. The method of claim 5 wherein said needles prior to the drying stepare replaced in a random manner on the anode; immersed a second time inthe electropolishing bath; and the polishing and rinsing steps arerepeated, after which the polished needles are dried.

7. A method for electropolishing a batch of surgical needles whichcomprises:

supporting a large number of randomly oriented needles in a magneticfield on a palladium anode; immersing said anode and needles supportedthereon in an electropolishing bath;

passing an electric current through the polishing bath and needles untilthe needles are polished;

removing the anode and the needles supported thereon from said polishingbath;

rinsing the needles;

removing the needles from the anode; and,

subsequently drying the polished needles.

8. The method of claim 7 wherein said needles prior to the drying stepare replaced in a random manner on the anode; immersed a second time inthe electropolishing bath; and the polishing and rinsing steps arerepeated, after which the polished needles are dried.

9. A method for electropolishing a batch of surgical needles whichcomprises:

supporting a large number of randomly oriented needles in a magneticfield on a rhodium anode;

immersing said anode and needles supported thereon in anelectropolishing bath;

passing an electric current through the polishing bath and needles untilthe needles are polished;

removing the anode and the needles supported thereon from said polishingbath;

rinsing the needles;

removing the needles from the anode; and,

subsequently drying the polished needles.

10. The method of claim 9 wherein said needles prior to the drying stepare replaced in a random manner on the anode; immersed a second time inthe electropolishing bath; and the polishing and rinsing steps arerepeated, after which the polished needles are dried.

11. A method for electropolishing a batch of surgical needles whichcomprises:

supporting a large number of randomly oriented needles in a magneticfield on an iridium anode; immersing said anode and needles supportedthereon in an electropolishing bath;

passing an electric current through the polishing bath and needles untilthe needles are polished;

removing the anode and the needles supported thereon from said polishingbath;

rinsing the needles;

removing the needles from the anode; and,

subsequently drying the polished needles.

12. The method of claim 11 wherein said needles prior to the drying stepare replaced in a random manner on the anode; immersed a second time inthe electropolishing bath; and the polishing and rinsing steps arerepeated, after which the polished needles are dried.

References Cited UNITED STATES PATENTS 2,803,595 8/1957 Anzaldi 2042973,038,475 6/1962 Orcutt 204142 3,268,428 8/1966 Buccino 204142 1,873,8268/1932 Devecis 204297 3,000,806 9/1961 Marotta et al. 204285 FOREIGNPATENTS 424,246 5/1933 Great Britain 204-297 546,465 2/1932 Germany204297 JOHN H. MACK, Primary Examiner T. TUFARIELLO, Assistant ExaminerUS. Cl. X.R.

mg? P 'EiNiTEE' smmmm @FFEQE ohhitmoim oi Qo-RRM' Pate 3,703, 52 i 1Data; November 21., 1972 Invent-017(8) Howard Beroff and Ernest L;Richmond It is" certified that error appears in the above-identifiedpatent and that said LettersPa-tenc are hereby ooi're cfied as shownbelow:

In Column 1*, line 62, "evently" should read evenly In Column 5, lihe 8"or--thophosphoric" should read orthophosphoric In Column 5, line 33,"ocntaining" should read containing Signd and sealed this 29th day ofMay 1973.

[SEALl Attestz o EDWARDMQFLETCHE R; ROBERT GOTTSCHALK Attesting Office-rCommissioner of Patents

